Method for personalizing an authentication token

ABSTRACT

An authentication token using a smart card that an organisation would issue to its customer, the smart card having a processor for executing a software application that is responsive to a user input to generate a one-time password as an output. The smart card co-operates with an interface device for inputting the user input and displaying the one-time password. The authentication token may be used in combination with a remote authentication server for validation of the password and hence authentication of the user.

The present application is a continuation of U.S. application Ser. No.12/978,754, filed Dec. 27, 2010 (U.S. Pat. No. 8,375,212); which is adivisional of U.S. application Ser. No. 10/176,974, filed Jun. 20, 2002(U.S. Pat. No. 7,865,738); which claims priority to Great Britain PatentApplication No. 0210692.0, filed May 10, 2002; all of which areincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an authentication token using a smartcard.

2. Description of the Prior Art

There are a variety of technologies available to authenticate remoteusers in order to enforce secure access control. These range fromsimple, single factor authentication (such as use of a password) tomultiple factor authentication (such as use of a physical token inconjunction with a Personal Identification Number (PIN)). It is widelyaccepted that single factor authentication offers limited assurance asit is vulnerable to a wide range of attacks, many of which are neithersophisticated nor expensive to mount (such as ‘shoulder surfing’ oreavesdropping). Most online services, however, still rely on singlefactor authentication because it appears to be the cheapest toimplement—although this is usually because the subsequent cost ofdealing with systematic attacks has not been considered.

Dual factor authentication systems are, however, widely used to protectremote access by support staff to these same online services. Manyorganisations also protect access to their critical corporate systems,both remotely and locally, using such authentication mechanisms. Theessence of a dual factor mechanism is that it requires both ‘somethingyou know’, for example, a PIN or passcode, and ‘something you have’, forexample a physical token that can be authenticated itself. Increasingly,research is being done to add a third type of factor, ‘something youare’ i.e. biometrics such as retina scan, iris scan or fingerprint, butthis is not yet available in a reliable cost-effective way that can beused reliably in a mass-market type environment.

There are a variety of tokens available that can fulfill the role of thesecond factor (‘something you have’), but many of them rely on aninfrastructure of interface devices to be able to authenticate them.Thus, use of a smart card requires a card reader to be available toenable the system to interact with the application resident on the smartcard. New form factors have been explored to reduce this reliance, suchas Universal Serial Bus (USB) tokens that can plug directly into a USBport on a computer. Many new PCs are being shipped with USB portsinstead of the older style serial ports or parallel ports, most notebookcomputers now only have USB ports and all Apple computers have hadeasily accessible USB ports since the launch of the iMac in 1998.

To remove the dependence on an external infrastructure and to enable thetoken to be used in as wide a range of channels as possible, a number ofmanufacturers have developed stand-alone tokens that do not need to beconnected to the remote computer system. They interact with the user viaa screen and keypad. The user then interacts with the remote systemthrough whatever channel they are using i.e. web, Wireless ApplicationProtocol (WAP) phone, voice, TV set-top box.

Stand-alone tokens generally offer one or more mechanisms by which theycan authenticate themselves to the remote system. One approach is forthe system to issue a ‘challenge’ to be entered into the token, forexample an apparently meaningless string of numbers. The token applies acryptographic process, using the challenge and other information that iskept secret inside the token. As a result, it generates a ‘response’,which is displayed to the user to be sent back to the remote system. Theremote system can check that the response received is the correctresponse from that token to the challenge sent and hence ascertain theauthenticity or otherwise of the token. This process may use a symmetriccryptographic process with keys that are shared between the token andthe remote system. Alternatively, it may use an asymmetric cryptographicprocess, removing the need for shared secret keys but requiringsignificantly more processing capability in the token. In most cases,the remote system does not generate the challenge and authenticate thetoken's response itself but uses a dedicated local authentication serverwhich is especially established for that purpose and can provide thefacility to multiple systems within the same organisation.

There is a variant on this approach where the challenge is generatedinternally to the token, based on a combination of static data,deterministically varying data (such as an event counter), and dynamicdata (such as time). The authentication server must be maintained insynchronisation with the token so that it can reproduce the samechallenge when it attempts to validate the response.

An alternative approach has been to use a modern version of the oldtried and tested method of having a series of passwords each of whichcan only be used once. This approach was used by the military for manyyears, supplying a pad of slips of paper, each of which had a one-timepassword printed on it. As each password was used it was ripped from thepad and discarded. A matching pad was maintained at the other end toenable messages to be validated. The modern approach is to use acryptographic process to generate a one-time password dynamically whenit is needed. The token and the authentication server share secretinformation that can be combined with dynamic information available toboth (for real-time systems this can be the time) enabling theauthentication server to be able to generate the same one-time passwordthat the token has generated and thus validate it. This mechanism uses asymmetric cryptographic process, which enables it to be carried outquickly and cost-effectively in the token. It does not require as muchprocessing at the authentication server as no challenge needs to begenerated at the outset, hence only a single interaction is neededbetween the protected system and the authentication server toauthenticate the user.

Smart cards are in use worldwide for a variety of purposes. They havelong been in use for financial products (credit, debit and loyaltycards), especially in France where they were invented. With the adventof GSM mobile phones, the smart card market has significantly increasedwith the need for Subscriber Identification Modules (SIMs). Thetechnology used on smart cards lags leading edge semiconductortechnology by 2 or 3 years, thus the speed and power of the processorsare relatively low and memory is restricted. As more ambitious uses aredevised for smart cards, the technology required is becoming morecomplex and hence the cost of the cards is increasing. Conversely, theincreasing size of the market has led to economies of scale in the mostwidely used technologies (such as those required for GSM SIMs or memorychips as used in digital cameras and MP3 players).

Asymmetric cryptographic functions are heavily processor intensive andhence significantly slower than symmetric functions (of the order of 100times slower). The limited processing capability of most smart cardchips has restricted their practical use to symmetric cryptographicfunctions. However, smart card chips are now available withcryptographic co-processors that can execute asymmetric cryptographicfunctions much more quickly enabling such functions to become apractical option. The newest versions of specifications such as EMV(credit/debit card functionality defined jointly byEuropay/Mastercard/Visa) take advantage of these improved capabilitiesto provide better security features.

Most smart cards have in the past been produced with a specific singleapplication hardwired into Read Only Memory (ROM). Internationalstandards (specifically ISO 7816) have established common specificationsfor smart cards, ranging from size and shape and where the contactsshould be, through the electrical characteristics, to the basiccommunications protocol to interact with the card and the underlyingfiling system structure that should be implemented on it. Somemanufacturers have produced simple proprietary operating systems tohandle all the standard activities (like the interface protocol) onbehalf of the applications. However, the smart card still has to behardwired at manufacture with the operating system software and theapplication software in the ROM. The standards allow for the applicationsoftware on the card to offer multiple separate ‘applications’ (such asa credit card, loyalty card and electronic purse) selectable by theinterface device with which the card is used. The required applicationis selected when the card is powered up and ‘reset’ by the interfacedevice and the appropriate interaction is then conducted with the card.However, these separate applications must all reside together in thesmart card's ROM and share the same data areas. Accordingly, they mustall trust each other to ensure that the data for one is not read oroverwritten by another. Generally, therefore, such cards will only haveseparate applications that have all been developed by (or for) the sameorganisation that is issuing the card.

To address these shortcomings, some multi-application smart cardoperating systems have been developed. These require only the operatingsystem to be hardwired into the smart card's ROM. Applications can beloaded into the card's Electrically Eraseable Programmable Read OnlyMemory (EEPROM) after manufacture. Indeed, they can be subsequentlyremoved or replaced allowing upgraded applications to be delivered ontothe smart cards even after they have been issued to end users. To ensurethat the applications can not interfere with each other, theapplications themselves are written in an interpreted language (such asJava) and the actual execution is under the control of the card'soperating system, thus allowing address range checking and othermechanisms to be used to isolate each application and its data. Theinitial cost of using such cards has led to a slow take up of thetechnology, but increasing capability of the card processors and largermemory is increasing their practical applicability. New GSM SIMs will beavailable on multi-application cards, allowing service operators tooffer customisable functionality on the SIM independent of theparticular phone in use, including value-added services.

The Applicant offers a remote authentication service under the nameQUIZID to enable users of a protected computer system (internal users orexternal customers) to be securely authenticated before being allowedaccess to the protected system. The current authentication mechanismrelies on a device (which must be ‘personalised’ and securely deliveredto the user) that generates one-time passwords; use of the device itselfis secured by the use of a colour-coded unique consumer code that mustbe entered by the user in order to obtain a password. The password and auser ID, entered into the protected system, are sent to QUIZID forvalidation and if a successful response is received the system can allowaccess to the user. A more detailed description of this can be found inPCT/GB01/05507. How the QUIZID service is used in relation to otheridentifying information such as account names or user identification isup to the designers of the protected system. The QUIZID service isdesigned to be used for protecting access to corporate systems as wellas publicly accessible systems such as e-tailers or financial services.

SUMMARY OF THE INVENTION

The present invention provides a design for a remote authenticationtoken using a smart card that an organisation would issue to itscustomer, along with an interface device to display the one-timepassword. In a preferred implementation, the invention is used incombination with a remote authentication server for validation of thepassword and is thus interoperable with the current QUIZID service.

As described above, many financial services are now issuing ‘smart’credit or debit cards which have already been personalised and securelydelivered to the customer. These same organisations are offering onlineservices that need effective user authentication to protect access tocustomer data as required by legislation. Consequently, forauthentication purposes, use of a smart card that has already beendelivered to the customer is cost-effective and will help to reinforceboth the organisation's brand and its commitment to security.

These and other objects of the present invention will be apparent fromreview of the following specification and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present invention will now be described in detail withreference to the accompanying drawings, in which:

FIG. 1 shows the distribution of components across the memory of amulti-application smart card;

FIG. 2 shows the interaction between a smart card and a personalisationdevice; and,

FIG. 3 shows the interaction between a smart card, an interface deviceand a user.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1 to 3 generally, we now describe the proposedtoken, including the components of the token, namely the smart carditself and the interface device. We also describe the operation of thetoken, including the end-user interaction with the token in normal use,the operation of the various components and the interaction betweenthem, and the handling of error conditions. The remote authenticationtoken proposed here combines the functionality of authenticationtechnology, including that provided by the existing QUIZID remoteauthentication service (described in more detail in PCT/GB01/05507),with the convenience of smart card technology. This type of technologyis either already in use or about to be launched by many organisations,especially in the financial services sector.

FIG. 1 shows an example of a smart card 10, which in common with manytypes of payment card displays account and issuer information 11, andalso contains a microchip 12. The chip 12 comprises various types of onboard memory, including ROM 13, EEPROM 14 and RAM 15, and also aprocessor 16. Thus, not only can information be stored on the card, butalso an application can be loaded onto the card issued by anorganisation to an end-user, for example a credit card with the EMVapplication. The card has already been personalised for the end-user bythe issuer and has been delivered to them by some secure means.

The smart card also contains the authentication application itself. Thisincludes the secret data that is used to generate the passwords and thecolour coded unique consumer code. Since the issuing organisation willalready be incurring the costs associated with issuing the smart cardthe additional costs to include the authentication application would berelatively low. The smart card may also contain one or more of theissuer's applications.

The authentication application may be loaded onto the card in one of twoways, depending on the type of smart card.

A ‘single application’ smart card will have the application and alimited operating system ‘burnt’ into the ROM 13 at chip manufacture. Inthis case a version of the authentication application will have beendeveloped in the appropriate language for the card's processor (whichmay be assembler or a higher level language depending on the chip andtool support). This version of the authentication application will besupplied to the issuer for examination and integration into the ROM maskto be hardwired into the card's chip 12. It may also be combined withthe issuer's application(s) prior to manufacture to make the ROM mask.Cards with the application already in the ROM 13 are delivered to theissuer. The card itself is then personalised by the issuer (embossingetc.) and the authentication application is personalised using aspecific personalisation device.

If the card is a multi-application card, the operating system will be‘burnt’ into the ROM 13 at chip manufacture. The authenticationapplication and any issuer applications will be subsequently loaded ontocard. Cards containing only the operating system are delivered to theissuer. The issuer's applications are loaded onto the card through aninteraction with the operating system. A version of the authenticationapplication will have been developed in the appropriate language for thecard's operating system (such as Java for Javacard or MEL for Multos)and then signed and certified. This version can be loaded at the sametime, separately or even subsequently, for example duringpersonalisation by the issuer. Once the authentication application hasbeen loaded it is personalised using a specific personalisation device.Although the multi-application operating systems allow for the loadingand personalisation of the authentication application after the card hasbeen issued, in the preferred embodiment it is not intended to issuecards prior to establishing the authentication application on them.

As indicated, whichever type of smart card 10 is used, the applicationwill be personalised to ensure the correct secret data is in the card'sEEPROM 14 along with an initial colour coded unique consumer code. Untilthe application is personalised it cannot be used. Once personalised itcannot be re-personalised. In the following embodiment, the application,once personalised will contain the following elements:

-   -   a secret key (SK) stored in EEPROM, used by the cryptographic        algorithm to generate passwords;    -   a unique consumer code stored in EEPROM, used to validate the        code entered by the user;    -   a monotonically increasing register (MIR) stored in EEPROM, used        by the cryptographic algorithm to generate passwords;    -   a seed value (V) stored in EEPROM, used by the key generation        algorithm; and,    -   application software to respond to application commands,        generate a password and generate a new key.

The application that is loaded onto the smart card operates in threemodes. Each mode allows a different limited range of interactions. Whenthe application is first loaded it is in Personalisation mode. In thismode it will respond only to a personalisation command. Afterpersonalisation the application is in Normal mode. In this mode it willinteract with an interface device to generate passwords when presentedwith a valid colour coded unique consumer code. If the incorrect uniqueconsumer code is entered in sequential attempts (beyond a pre-set limit)the application enters Locked mode. In this mode the application willonly accept (a limited number of) attempts to enter the correct unlockcode. If the correct unlock code is entered, the application reverts toNormal mode. The application can never be returned to Personalisationmode.

When the application is loaded onto the smart card it is in anon-personalised state. The secret data has been set to starting values,but the unique key for the card has not been set. The card itself does,however, have a unique serial number. The application is inPersonalisation mode. It will not accept any commands from a user'sinterface device in this mode. It will, however, accept apersonalisation command from a personalisation device. Thepersonalisation device requests the serial number, and establishes aprivate communications channel with the application to enable it toissue the application with seed values for the secret key and the keygeneration algorithm. The same data is stored securely by thepersonalisation device for subsequent loading into the authenticationserver. The card serial number can be used to determine the usernamethat the issuer will associate with the card. Once the seed has beenused by the application to set the initial secret key, the applicationswitches to Normal mode.

While there are a variety of suitable mechanisms to secure thecommunications between the personalisation device and the application,the preferred implementation is to use a key exchange protocol toestablish a transport key, supplemented by a pre-defined personalisationkey to protect against ‘man in the middle’ attacks. This is necessarybecause, although the card may be personalised at the same time that itis loaded with the application, in a multi-application card environmentthis may be subsequent to the manufacture or issuer personalisation ofthe card. It may even be performed remotely from the personalisationdevice, which could be at (or incorporated into) the authenticationserver, and must therefore be protected against interception.

An example of a personalisation interaction is illustrated in FIG. 2 andthe steps involved are described below:

-   -   initially, the card is reset (step 200) and responds with an        Attention to Reset (ATR).    -   the personalisation device selects (step 201) the authentication        application and determines (step 202) that it is in        personalisation mode.    -   the personalisation device requests (step 203) the card serial        number and receives (step 204) the serial number (SN) and a        challenge (C) from the card application.    -   using the pre-defined Personalisation Key (PK) the        personalisation device encrypts (step 205) SN and C and returns        the encrypted value to the card in a request to commence        initialisation.    -   the card application decrypts (step 206) the received data using        PK and validates it as correct. This demonstrates that both the        card application and the personalisation device are using the        correct PK.    -   if successful, the card application uses (step 206) the key        exchange protocol to generate messages to send back to the        personalisation device. The key exchange protocol itself is        inherently protected against interception, but the messages are        also encrypted (step 206) using PK to protect against ‘man in        the middle’ attacks.    -   the personalisation device responds (step 207) with the        appropriate key exchange protocol messages, encrypted using PK.    -   at the end of the key exchange, both the card application (step        208) and the personalisation device (step 209) have a unique        shared key that is unknown to anyone else including        eavesdroppers. This key is used as a Transport Key (TK) for the        rest of the personalisation process.    -   the card application generates a request (step 208) (R) for its        Secret Key (SK), encrypts (step 208) the request using TK and        sends it to the personalisation device.    -   the personalisation device decrypts (step 210) the request using        TK and validates it as correct. This demonstrates that both the        card application and the personalisation device are using the        same TK and hence that the key exchange process has worked        correctly.    -   if successful, the personalisation device generates (step 210),        or obtains from a pre-generated list, the Initial Secret Key        (ISK) and the Initial Value (IV) for the card application's key        generation seed (V). ISK and IV are encrypted (step 210) using        TK and sent to the card.    -   the card application decrypts (step 211) the received data using        TK, initialises (step 211) its SK to ISK and initialises (step        211) its V to IV. The card application now enters Normal mode.    -   the personalisation device delivers (step 210) the ISK and IV to        the authentication server (if they were not pre-generated and        hence already in the authentication server) securely.

Although there may be a number of suitable key exchange protocolsavailable, the preferred implementation is to use the Diffie-Hellmanexchange which is within the processing capabilities of the card anddoes not rely on out of band secure communications to pre-establish anyshared secret. The Diffie-Hellman exchange operates as follows:

-   -   the card application and personalisation device both know the        pre-defined values ‘n’ (a large prime number) and ‘g’ (a small        single digit number that is primitive mod n). These don't need        to be kept secret and can be common to all cards, therefore are        included in the application that is loaded onto the card;    -   the card application generates a large random integer ‘x’;    -   the card application calculates A=g.sup.x mod n;    -   the card application sends A to the personalisation device;    -   the personalisation device generates a large random integer ‘y’;    -   the personalisation device calculates P=g.sup.Y mod n;    -   the personalisation device send P to the card application;    -   the card application calculates K1=P.sup.x mod n;    -   the personalisation device calculates K2=A.sup.y mod n; and,    -   both K1 and K2 are equal to g.sup.xy mod n and hence the card        application and the personalisation device have calculated the        same key which can now be used as the Transport Key (TK).

The second main component of the authentication token is the interfacedevice provided to the end-user. The interface device is a device thatcan be used with a user's smart card to enable the generation of apassword. The device could take a variety of forms, for example a pen ora calculator or a mobile phone battery pack. When the smart card isinserted into the interface device, the user is prompted to enter theircolour coded unique consumer code and, if correct, the output responsefrom the interface device is a one-time password. A password sogenerated can then be entered into the access device, such as a PC, atelephone, a WAP phone, or even by voice, for the service that requiresthe authentication.

As the smart card is personalised to the customer, the interface devicedoes not need to be. Users, therefore, can share an interface device,for example one at home for use by all members of a family. Equally,users can have more than one, for example one at home, one in theoffice. Users can even, safely, borrow an interface device from astranger, for example in a cybercaf or a restaurant. Therefore, in oneembodiment, the interface devices are preferably generic, hence allidentical and requiring no personalisation for each customer. As they donot need to be personalisable or securely delivered to users (they couldeven be available over the counter if the issuing organisation has abranch network), it should be possible to keep the associated costsignificantly low.

The interface device provides the power to the smart card to enable itto operate. It also includes a real-time clock to enable time to be usedas a dynamic input into the password generation process. It thereforeincludes a battery, which has a reasonably long life but is notaccessible by the user. After manufacture, the device's clock can besynchronised with the service's system-wide time through the smart cardinterface. When battery replacement is required, the device's clock mustonce again be synchronised (which is why the battery is notuser-replaceable). When no smart card is inserted in the slot, thedevice only provides power to the real-time clock. When a smart card isinserted, the device powers up and applies power to the smart card andto itself. When the smart card is removed the device powers down. Forthis reason, the device needs no user accessible power switch.

Although the interface device may take one of many forms, it willtypically include the following five elements:

-   -   i. an interface to the token, initially a set of smart card        contacts, but other interfaces would be possible, such as        Bluetooth;    -   ii. an input mechanism, such as a keypad for entry of the colour        coded unique consumer code and for menu selection;    -   iii. an output mechanism, such as a display screen, although        other mechanisms could be provided such as voice output for the        blind;    -   iv. a source of a dynamic input to the password generation, such        as a battery operated real-time clock; and,    -   v. a processor with application software to handle the        interfaces.

Once the user has received the smart card and an interface device theycan use the combination to authenticate themselves to the issuer'sservices, as and when required. The authentication is assured either byan authentication server operated by the issuer themselves or by ashared authentication server such as described in PCT/GB01/05507.

There are many different business models within which strongauthentication would be advantageous. An example is given below of atypical interaction, where the issuer provides an online e-commerceservice requiring the users to authenticate themselves when they placean order.

-   -   1. User browses issuer's online service on their PC.    -   2. User places order on service.    -   3. Service prompts user for authentication password in secure        form.    -   4. User inserts smart card into an interface device.    -   5. Interface device prompts for colour coded unique consumer        code entry.    -   6. User enters colour coded unique consumer code into the        interface device.    -   7. Interface device displays password.    -   8. User enters password into secure form on issuer's online        service on their PC.    -   9. Service authenticates password with remote authentication        service.    -   10. Service confirms authentication to user, accepts order.    -   11. User removes the smart card from the interface device.

When the smart card is issued to the user, the application will havebeen personalised and will be in Normal mode. The user can then use ageneric interface device to change the colour coded unique consumer codefrom the pre-set initial value to one of their own choice. The card willnow be able to interact with a generic interface device to generate apassword. An example of this type of interaction is shown in FIG. 3.

The process used to generate the one-time password relies on the use ofa secret key (SK) in conjunction with a tried and tested cryptographicalgorithm. The data that is processed by the algorithm to generate thepassword is derived from a Monotonically Increasing Register (MIR) thatis maintained within the card application and tracked at theauthentication server, along with a Dynamic Variable (DV) that can bevalidated or reproduced at the authentication server. To increase thevariability of the passwords and the difficulty of an attempt to spoofthe password generation, the secret key is itself modified after eachpassword generation using a key generation algorithm. The authenticationserver must apply the same algorithms to validate the password and keepin synchronisation with the MIR, SK and V on the card.

The process for password generation is as follows:

-   -   the MIR is concatenated with the DV to produce a payload (L);    -   L is encrypted using the cryptographic algorithm with SK to        produce G;    -   the least significant bits of G are used to generate an integer        I;    -   the least 2 significant bits of DV, concatenated with the least        significant bit of MIR, are used to generate an integer D;    -   I is combined with D to produce the password;    -   the key generation algorithm uses MIR and SK and a seed V to        generate a new key NK and a new seed NV;    -   SK is replaced with NK;    -   V is replaced with NV; and,    -   MIR is incremented.

The inclusion of the 3 bits that are used to create D, enables theauthentication server to detect loss of synchronisation with theapplication on the card. The authentication server will be maintainingits own copy of the MIR for each card. When the password arrives to bevalidated at the authentication server, the least significant bit of theMIR on the card, as included in the password via D, should match that ofthe MIR in the server. If not, there may have been a previous passwordgenerated that did not arrive at the server, in which case the serverincrements the MIR and executes the key generation algorithm to obtainthe appropriate SK. Similarly, the 2 least significant bits of the DVincluded in the password via D can be compared with those of the DVreproduced at the authentication server, allowing for a discrepancy tobe detected and corrected before the password is validated. Parameterscan be established at the authentication server to determine whether(and how many) subsequent values of the MIR should be tried if thevalidation fails.

The combination of I and D can be achieved in a variety of ways. The 3bits of D can be interspersed at pre-determined positions in I, theresulting value then being interpreted as a decimal value. Any lengthpassword can be generated by selecting the appropriate number of bits ofthe output of the cryptographic algorithm, for example an eight digitpassword would be produced from a 26 bit value composed of the 3 bits ofD and 23 bits of I. Alternatively, I can be interpreted as a decimalvalue (the length depending on the number of bits used) and Dinterpreted as a decimal value (one digit in length as only 3 bits areused). The resulting password would be created by concatenating thedigits derived from I with the digit derived from D (or inserting thedigit from D into the digits from I). Again, any length password can begenerated by selecting the appropriate number of bits of the output ofthe cryptographic algorithm. An eight digit password would require 23bits to be used to produce I which would be 7 digits long, with Dproviding the eighth digit. In the preferred embodiment, an eight digitpassword will be generated by interpreting 23 bits of the cryptogram asa 7 digit decimal integer I and appending a decimal digit interpretedfrom the 3 bits of D.

The preferred implementation is to use the Advanced Encryption Standard(AES) with 128 bit keys as the cryptographic algorithm, along with a keygeneration algorithm based on ANSI X9.17 but using AES and generating128 bit keys. One of the strengths of AES is that there are no knownweak keys, so all keys generated by the key generation algorithm wouldbe acceptable.

As each card must work with any one of the interface devices, the sourceof the DV in the initial embodiment will be a real-time clock in theinterface device. In future embodiments, when the smart card may haveit's own source of power, there will be other sources of dynamicvariable that could be maintained within the card itself.

The example shown in FIG. 3 illustrates the case where the user entersthe unique consumer code correctly first time. If the unique consumercode entered is incorrect the application will respond ‘code incorrect’and the interface device will re-prompt for the unique consumer code.This can happen repeatedly up to a preset limit, for example threeattempts. If the unique consumer code has not been entered correctlywithin the limited number of attempts, the application will respond‘Locked’ and the interface device will inform the user that theapplication is locked. The application will enter Locked mode.

When the application is in Locked mode it will not accept commands togenerate a password. It will not respond to the normal interactions.When the interface device attempts to interact with the application, itis told (in the Answer To Reset) that the application is locked andinforms the user that the application is locked. If the user then entersa sequence of colour codes the interface device will send them to theapplication as an unlock command. The correct sequence will cause theapplication to unlock and revert to Normal mode. To obtain the correctsequence the user will have to contact a customer support function. Theunlock sequence will only work once. If the application is subsequentlylocked again a different unlock sequence will be required.

Other embodiments of the invention will be apparent to those skilled inthe art from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

I claim:
 1. A method for personalizing an authentication tokenresponsive to a user input from an authentication token interface deviceto generate a secure password comprising: requesting from theauthentication token, by a personalization device in communication withthe authentication token, a serial number of the authentication token;establishing an encrypted session between the authentication token andthe personalization device upon receipt of the serial number; sending,by the personalization device to the authentication token, an initialseed value and an initial secret key responsive to authentication of theserial number; storing, by the personalization device, the initial seedvalue and the initial secret key; and, transferring, by thepersonalization device to the authentication token, the initial seedvalue and the initial secret key used by the authentication token togenerate the secure password.